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Huang Y.,Control Iron and Steel Research Institute, China | Huang Y.,Beijing Harmofinery Technology Co. | Chen Z.,Control Iron and Steel Research Institute, China | Chen Z.,Advance Technology and Materials Co. | And 11 more authors.
Chemistry Bulletin / Huaxue Tongbao | Year: 2014

Through comparative studying on LiFePO4/C preparation process of adding carbon source in precursor and pre-sintered material, marked as LFP-1 (in-situ carbon coating) and LFP-2 respectively, by means of C-S test, XRD, SEM, BET, Raman, the effects of carbon content, morphology, particle size and surface carbon structure on the electrochemical performance of LiFePO4/C cathodes were investigated. SEM images showed that particle sizes of LFP-1 and LFP-2 are about 10μm and 100nm respectively. The EIS and galvnostatic charge-discharge tests indicated that LFP-1 has lower charge transfer resistance (Rct), better rate and cycle performance than that of LFP-2, which can be attributed to the different microstructure and the higher degree of graphitized carbon of LiFePO4/C. Raman spectroscopic analysis showed that the ratio of the ID/IG and Asp3/Asp2 of LFP-1 is lower that of LFP-2, which means the degree of graphitized carbon of LFP-1 is higher than that of LEP-2. These results have important significance for improving the overall performance of olivine cathode materials for lithium ion batteries.

Zhang Y.,Beijing Harmo FinerY Technology Co. | Liu Z.,Beijing Harmo FinerY Technology Co. | Liu Z.,Advanced Technology and Materials Co. | Xia J.,Beijing Harmo FinerY Technology Co. | And 3 more authors.
Materials Science Forum | Year: 2011

LiFePO4/C composite with different types of organic carbon sources has been synthesized by carbon thermal reduction technique. The physical characteristics and electrochemical properties of LiFePO4/C composite have been studied compared with commercial products. It is shown that good carbon-coated LiFePO4/C composite can be obtained with 13wt.% glucose as carbon source, which has effected on the good processing performance due to its suitable specific surface area of 26.3m2/g and high tap density of 1.3g/cm3. Furthermore, it has contributed to the high-rate electrochemical property with discharge capacity of 128mAh/g at 1C (1C=170 mAh/g). © (2011) Trans Tech Publications.

Huang Y.,Beijing Harmofinery Technology Co. | Yang K.,Beijing Harmofinery Technology Co. | Xie Y.,Beijing Harmofinery Technology Co. | Wang T.,Beijing Harmofinery Technology Co. | Wu J.,Beijing Harmofinery Technology Co.
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society | Year: 2011

The effects of partially substituting Y for La on the crystal structure as well as on the electrochemical properties of the La0.75-xYxMg0.25 Ni3.17Al0.13 and La0.75-xYxMg0.25 Ni3.37Al0.13 (x=0.00, 0.05, 0.10) were investigated by means of powder X-ray diffraction (XRD) and electrochemical measurements. The XRD results suggested that the La0.75-xYxMg0.25 Ni3.17Al0.13 were mainly composed of Ce2Ni7-type structure, while the La0.75-xYxMg0.25 Ni3.37Al0.13 were mainly composed of Pr5Co19-type structure. By the partially substitution, the activity times and discharge capacity were changed slightly. The Y substitution for La would deteriorate the cycle stability, but raise the desorbing plateau pressure, and the effects of those alterations were different in each structure. In La0.75-xYxMg0.25 Ni3.17Al0.13 (Ce2Ni7-type), the S80% decreased from 222 cycles (x=0.00) to 112 cycles (x=0.10), whereas the desorbing plateau pressure rose from 0. 015 MPa (x=0.00) to 0.045 MPa (x=0.10) accordingly. In La0.75-xYxMg0.25 Ni3.37Al0.13 (Pr5Co19-type), the S80% decreased from 172 cycles (x=0.00) to 127 cycles (x=0.10), whereas the desorbing plateau pressure rose from 0.019 MPa (x=0.00) to 0.076 MPa (x=0.10) accordingly.

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